d and f Block Elements — Page 26 | JEE Chemistry

Q251

In metallurgy the term "gangue" is used for :

A Contamination of undesired earthy materials.

B Contamination of metals, other than desired metal.

C Minerals which are naturally occurring in pure form

D Magnetic impurities in an ore.

Correct Answer

Option A

Solution

Earthy and undesired materials present in the ore other then the desired metal is known as gangue.

Q252

Which one of the following statements is incorrect?

A Cast iron is obtained by melting pig iron with scrap iron and coke using hot air blast.

B The malleable iron is prepared from cast iron by oxidising impurities in a reverberatory furnace.

C van Arkel method is used to purify tungsten.

D Boron and Indium can be purified by zone refining method.

Correct Answer

Option C

Solution

Option A: Cast iron is obtained by melting pig iron (crude iron) with scrap iron and coke (a fuel made from coal) using a hot air blast.

The resulting molten metal is poured into molds to form cast iron products.Option B: Wrought Iron or Malleable iron is produced from cast iron by heating it in a reverberatory furnace lined with Haematite, which removes impurities through oxidation.

The resulting product is malleable iron, which is a type of iron that can be shaped and molded.

Option C: van Arkel Method for Refining Zirconium or Titanium: This method is very useful for removing all the oxygen and nitrogen present in the form of impurity in certain metals like $\mathrm{Zr}$ and Ti.

The crude metal is heated in an evacuated vessel with iodine.

The metal iodide being more covalent, volatilises:

\mathrm{Zr}+2 \mathrm{I}_2 \rightarrow \mathrm{ZrI}_4

The metal iodide is decomposed on a tungsten filament, electrically heated to about $1800 \mathrm{~K}$ .

The pure metal deposits on the filament.

\mathrm{ZrI}_4 \rightarrow \mathrm{Zr}+2 \mathrm{I}_2

Option D: Zone refining is a method used to purify certain metals such as boron, indium, germanium, silicon, and galium.

It involves heating the metal to a liquid state and then slowly moving it along a column to allow impurities to migrate to one end of the column, where they can be removed.

Q253

Given below are two statements: one is labelled as Assertion A and the other is labelled as Reason R Assertion A: In an Ellingham diagram, the oxidation of carbon to carbon monoxide shows a negative slope with respect to temperature. Reason R: CO tends to get decomposed at higher temperature. In the light of the above statements, choose the correct answer from the options given below

A A is correct but R is not correct

B Both A and R are correct but R is NOT the correct explanation of A

C A is not correct but R is correct

D Both A and R are correct and R is the correct explanation of A

Correct Answer

Option A

Solution

2 \mathrm{C}(\mathrm{s})+\mathrm{O}_2(\mathrm{~g}) \rightarrow 2 \mathrm{CO}(\mathrm{g})

$\Delta_{\mathrm{r}} \mathrm{S}^0$ is $+v e, \Delta_{\mathrm{r}} \mathrm{G}^0=\Delta_{\mathrm{r}} \mathrm{H}^0-\mathrm{T} \Delta_{\mathrm{r}} \mathrm{S}^0$ ; Thus slope is negative.

As temperature increases $\Delta_{\mathrm{r}} G^{\mathrm{o}}$ becomes more negative thus it has lower tendency to get decomposed.

Q254

The methods NOT involved in concentration of ore are A. Liquation B. Leaching C. Electrolysis D. Hydraulic washing E. Froth floatation Choose the correct answer from the options given below :

A A and C only

B C, D and E only

C B, D and C only

D B, D and E only

Correct Answer

Option A

Solution

Methods involved in concentration of one are (i) Hydraulic Washing (ii) Froth Floatation (iii) Magnetic Separation (iv) Leaching

Q255

Given below are two statements: Statement I: During Electrolytic refining, the pure metal is made to act as anode and its impure metallic form is used as cathode. Statement II: During the Hall-Heroult electrolysis process, purified

\mathrm{Al}_{2} \mathrm{O}_{3}

is mixed with

\mathrm{Na}_{3} \mathrm{AlF}_{6}

to lower the melting point of the mixture. In the light of the above statements, choose the most appropriate answer from the options given below:

A Statement

\mathrm{I}

is correct but Statement II is incorrect

B Statement I is incorrect but Statement II is correct

C Both Statement I and Statement II are incorrect

D Both Statement I and Statement II are correct

Correct Answer

Option B

Solution

During electrolytic refining, the pure metal is made to act as cathode and impure metal used as anode.

Q256

In the extraction of copper, its sulphide ore is heated in a reverberatory furnace after mixing with silica to:

A remove

\mathrm{FeO}

as

\mathrm{FeSiO}_{3}

B remove calcium as

\mathrm{CaSiO}_{3}

C decrease the temperature needed for roasting of

\mathrm{Cu}_{2} \mathrm{~S}

D separate

\mathrm{CuO}

as

\mathrm{CuSiO}_{3}

Correct Answer

Option A

Solution

\mathrm{\mathop {FeO}\limits_{Basic} + \mathop {Si{O_2}}\limits_{Acidic} \overset{{}}\longrightarrow \mathop {FeSi{O_3}}\limits_{(Slag)}}

Q257

The reaction representing the Mond process for metal refining is _________.

A

\mathrm{ZnO+C\overset{\Delta}\longrightarrow Zn+CO}

B

\mathrm{2K[Au(CN)_2]+Zn\overset{\Delta}\longrightarrow K_2[Zn(CN)_4]+2Au}

C

\mathrm{Zr+2I_2 \overset{\Delta}\longrightarrow ZrI_4}

D

\mathrm{Ni+4CO\overset{\Delta}\longrightarrow Ni(CO)_4}

Correct Answer

Option D

Solution

Mond process is need for the purification of $\mathrm{Ni}$ metal

\begin{aligned} & \therefore \underset{\text{ (impure) }}{\mathrm{Ni}}+4 \mathrm{CO} \stackrel{330-350 \mathrm{k}}{\longrightarrow} \mathrm{Ni}(\mathrm{CO})_{4} \\\\ & \mathrm{Ni}(\mathrm{CO})_{4} \stackrel{450-470 \mathrm{k}}{\longrightarrow} \underset{\text{ (pure) }}{\mathrm{Ni}}+4 \mathrm{CO} \end{aligned}

Q258

Which one of the following is not an example of calcination?

A

\mathrm{CaCO}_{3} \cdot \mathrm{MgCO}_{3} \stackrel{\Delta}{\longrightarrow} \mathrm{CaO}+\mathrm{MgO}+2 \mathrm{CO}_{2}

B

2 \mathrm{PbS}+3 \mathrm{O}_{2} \stackrel{\Delta}{\longrightarrow} 2 \mathrm{PbO}+2 \mathrm{SO}_{2}

C

\mathrm{CaCO}_{3} \stackrel{\Delta}{\longrightarrow} \mathrm{CaO}+\mathrm{CO}_{2}

D

\mathrm{Fe}_{2} \mathrm{O}_{3} \cdot \mathrm{xH}_{2} \mathrm{O} \stackrel{\Delta}{\longrightarrow} \mathrm{Fe}_{2} \mathrm{O}_{3}+\mathrm{xH}_{2} \mathrm{O}

Correct Answer

Option B

Solution

Calcination is the process of heating a solid material in the absence of air or with limited air to remove volatile components or to cause thermal decomposition.

Among the given reactions: (A) $\mathrm{CaCO}_3 \cdot \mathrm{MgCO}_3 \stackrel{\Delta}{\longrightarrow} \mathrm{CaO}+\mathrm{MgO}+2 \mathrm{CO}_2$ is an example of calcination, where a mixture of calcium carbonate and magnesium carbonate is heated to produce calcium oxide, magnesium oxide, and carbon dioxide.

(C) $\mathrm{CaCO}_3 \stackrel{\Delta}{\longrightarrow} \mathrm{CaO}+\mathrm{CO}_2$ is an example of calcination, where calcium carbonate is heated to produce calcium oxide and carbon dioxide.

(D) $\mathrm{Fe}_2 \mathrm{O}_3 \cdot \mathrm{xH}_2 \mathrm{O} \stackrel{\Delta}{\longrightarrow} \mathrm{Fe}_2 \mathrm{O}_3+\mathrm{xH}_2 \mathrm{O}$ is an example of calcination, where hydrated iron(III) oxide loses water molecules to form anhydrous iron(III) oxide.

However, (B) $2 \mathrm{PbS}+3 \mathrm{O}_2 \stackrel{\Delta}{\longrightarrow} 2 \mathrm{PbO}+2 \mathrm{SO}_2$ is not an example of calcination.

This reaction is an example of roasting, a process in which a sulfide ore is heated in the presence of air to convert it into its oxide and release sulfur dioxide gas.

Roasting is typically used for metal extraction from sulfide ores.

So the correct answer is: (B) $2 \mathrm{PbS}+3 \mathrm{O}_2 \stackrel{\Delta}{\longrightarrow} 2 \mathrm{PbO}+2 \mathrm{SO}_2$

Q259

Given below are two statements related to Ellingham diagram: Statement I : Ellingham diagrams can be constructed for formation of oxides, sulfides and halides of metals. Statement II : It consists of plots of

\Delta_{\mathrm{f}} \mathrm{H}^{0}

vs

\mathrm{T}

for formation of oxides of elements. In the light of the above statements, choose the most appropriate answer from the options given below:

A Both Statement I and Statement II are correct

B Both Statement I and Statement II are incorrect

C Statement I is correct but Statement II is incorrect

D Statement I is incorrect but Statement II is correct

Correct Answer

Option C

Solution

Statement I is correct, Ellingham diagram can be constructed for formation of oxides, sulphides and halides of metals.

(As per NCERT) Statement II is incorrect because Ellingham diagram consists of $\Delta_t G^0$ vs $T$ for formation of oxides of elements.

Q260

Which one of the following is most likely a mismatch ?

A Titanium - van Arkel Method

B Zinc - Liquation

C Nickel - Mond process

D Copper - Electrolysis

Correct Answer

Option B

Solution

The most likely mismatch among the given options is : Zinc - Liquation.

Liquation is a process of refining metals that involves melting the metal at a temperature slightly below its melting point and allowing it to cool slowly.

This causes impurities to separate out as they solidify at different temperatures from the main metal.

Liquation is typically used for metals with low melting points, such as tin and lead.

Zinc, on the other hand, has a relatively high melting point of 419.53 °C.

Therefore, it is unlikely that zinc would be refined using the liquation process.

Instead, zinc is commonly produced through the electrolysis of its ores or by distillation in the retort process.

On the other hand, the other options are more likely to be matched with their respective refining processes: - Titanium is commonly refined using the van Arkel method, which involves the reaction of titanium tetrachloride with a metal like sodium or magnesium to form a volatile titanium compound that can be purified through fractional distillation. - Nickel is commonly refined using the Mond process, which involves the reaction of nickel with carbon monoxide to form a volatile nickel carbonyl compound that can be purified through fractional distillation. - Copper is commonly refined using electrolysis, which involves the use of an electric current to separate copper from other metals in an electrolyte solution.

Therefore, the most likely mismatch among the given options is Option B - Zinc - Liquation.